Recently there has been a propagation of calls using Voice over Long Term Evolution (VOLTE) standards. That, combined with the continued increase in cellular network telecommunications traffic, has incentivized some service providers to offer calling through WiFi connections in accordance with the various IEEE 802.11 standards. Such WiFi offloading, as it is called, enables telecommunications calls and data from a mobile device to be offloaded from the cellular network to the internet for transport from the mobile device to the termination destination point and vice versa. Such WiFi networks may be either generally secure, operator controlled networks, known as trusted networks, or generally unsecured, publicly accessible WiFi networks through public hotspots and the like, known as untrusted networks.
Call continuity between trusted/untrusted WiFi networks and Long Term Evolution (LTE) networks is provided for in the various 3GPP specifications. VOLTE governs the movement of mobile devices between the WiFi and LTE networks with a call in progress.
However, the same flexibility in moving between WiFi and LTE networks does not currently exist for emergency calls. There is a need to provide a similar calling experience for users making emergency calls.